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CHAPTER 4

Data processing and other instructions

The AArch64 processor provides a rich set of data processing instructions, most of which
perform arithmetic or bitwise logical operations. There are also a few special instructions that
are used infrequently to perform operations that are not classiﬁed as load/store, branch, or
data processing.

The data processing instructions cannot access data stored in memory. They operate only
on CPU registers, and possibly immediate data that is encoded as part of the instruction. In
general, data must ﬁrst be moved from memory into a CPU register before processing can be
performed. The most common way to move data from memory into registers and vice versa is
by using the load and store instructions, which are covered in Chapter 3. Each data processing
instruction performs one basic arithmetic or logical operation. The instructions are grouped in
the following categories of operations:
• Arithmetic
• Logical,
• Data Movement,
• Multiplication,
• Division,
• Comparison,
• Conditional, and
• Special.

4.1 Operand2

Most of the data processing instructions require the programmer to specify two source
operands and one destination register. Because three items must be speciﬁed for these in-
structions, they are known as three address instructions. The use of the word address in this
case has nothing to do with memory addresses. The term three address instruction comes
from earlier processor architectures that allow arithmetic operations to be performed with data
that is stored in memory rather than registers.
Referring back to Fig. 3.1, the ﬁrst source operand speciﬁes a register whose contents
will be supplied from the register ﬁle on the A Bus and enter the ALU. The second source

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